Oh right! Mine have grit mixed into their food already but it's optional, no need to run out buying 7lbs. Of it worrying your ducks won't make it without grit (hahaha well I guess EVERYONE needs grit to make it through lifeI'm killing myself here with these puns)
Hmmm, I have read that there is a risk of impaction if they don't get grit - - - and I agree, no need to buy 7 pounds of it. If you don't use poisons and fertilizers on your lawn, you can dig up a little soil with some grass and put it in a bowl for the ducklings to play with - they will ingest some grit from that. Or a teaspoon of clean play sand or builders sand, I am told.